Please note that this product has been placed on legacy status. This means that it is still manufactured but is not recommended for newer designs.
The only difference between a G340 and a G320 is the step pulse multiplier. This is only useful for high count encoders or low step pulse frequencies. The step pulse multiplier effectively acts as an encoder divider, dividing your encoder line count by 1, 2, 5, or 10. The COMMON input on the G340 is also user settable to be either COMMON ground or COMMON +5V as opposed to the default COMMON +5V on the G320.